Planimeter



Feb. 9 1926. 1,572,132

|... LARRAZABAL Y FERNANDEZ PLANIMETER Filed Dec. 5. 1922 DEE-m .%\'N 3""% M;

curved edge Patente- EE STATEIF:

LUIS LARRAZABAL Y FERNANDEZ,'Ol HABANA, CUBA.

PLANIMETEE;

Application filed December 5, 1922. Serial No. 605,118.

To 75 107mm it only concern.

Be it known thnt I, LUIs LARRAZABAL Y hnnNANnnz, a citizen of the Republic of Cuba. and resident of Habana, Cuba (whose postal address is Villegas No. 106, Habana, subs), huve l11\ 011l6 (l'01'l'2lll1 new and useful improvem nts in Plunimeters, of which the following is a specification. This invention relates to planinieters or instruments tor measuring; surfaces and its object is toetiect improvements in the construction of the some whereby the same is rendered stable, may be readily manufactured at small cost, and may be readily operetc-d.

llith the s eeve and other objects in view the invention consist." in the construction, combination and arrangement of devices hereinafter described and claimed.

The invention is described with reference to the figures ot the annexed drawings, in which:

F tie a front elevation of e. planimeter pro vul'ed with the improvement forming the sub ect matter of this invention.

i2 is an upper plan viewo't same.

Fig. 3 is a cross vertical section on line -:l----; of Figs. 1 and 2.

Fig. 4 a. cross vertical section on line 5- 5 of Figs. 1 and 2.

' the drawings, 1 indicates the main body ot no pluniineter consisting or": a polished steel bar having at one of its ends a stand in the shape of a spatula 2 of sharp slightly v 2 whose plane coincident with that ot the body 1 and the stand 2. The other end of the ma' 1 body 1 terminate n, n extension o't vertical cylindrical form 3 h a vertical opening i. In this opening t. litly re:eived the reduced upper end 5 oi the stem of the needle 5 which has a. dull tip and presents at the point where the tapering 5' commences a rim 6 which act as u butt against the lower face of the extension 3. The cylindrical portion of the stem of needle 5, which is below the rim 6, extends through an opening 7 of a collar 8, which is secured in place and in which terminates a curved arm 9 which projects upwardly from :1 side of aring 1.0 concentric with the tip of the needle 5 and which forms it supportin base for the planimeter, around the nezdle 5, so thntthe lower face of the ring 10 may come in level-with the dull tip of the needle 5, the ring 16) being provided with three qiiiftl stiu tliee s 1 in the rc o th ring 10. The axial line 01 collar 8 coincides with the vertical Sllttfft of the ring 10 and the arm 9 hes in the vertical plane of the main body 1, the needle 5 and the spatula 2.

In u preferred form of the invention the ring 10 presents at its upper inner edge u beveled cut 10 Such construction causes the needle 5 to have a certain stability on the plan of a drawinq, afforded by the supporting. base formed by the ring 10, this arrangement permittingthe plunimeter to stand on a plan by bearing three points which are not in a straight line and which is constituted by said ring 10 and the tangency or lower point in the lower sharp edge 2' 0t spatula 2.

In order to deter iine with this plnniine- 'er the surtuce limited by a closed border drawn on a paper, for instance, the planinieter is placed in raised position on the plane of the paper so that the tip of needle 5 may come on the gravity center of the closed surface or approximately on same it such center is not known, and this point is then united by a straight line with any point whatever of the border. Then there is marked on the paper the position of the spatula 2, which can be any position, to effect which a slight pressure will be exerted on the planim tcr, which produces on one previously occupied and this second place is marked on the paper by means of a slight pressure on the planimeter, as before. The distance traveled by the spatula, that is, the distance between the initial and final positions of the lower point of the spatula, multiplied by the distance between the tip of the needle 5 and the lower point of the spatula (which isthe constant of the instrument) will give the area. of the surface limited by the closed border.

()nce this first operation is finished, the planimeter is rotated on the tip of the needle 5 an angle of 180 and the same op eration as previously explained is repeated to obtain another figure of the area of the surface. The arithmetical half or average of the two figures gives the actual value of the sought area. In orde'r'to assure the accuracv of the result, the operation can be repeated various times and the average is taken as an accurate value;

It should be understood that the details of construction of the instrument and its form can he Widely varied Without departing from the essence or spirit of the inven tion. which is as pointed out in the appended claims.

That I claim is 1. A plannneter comprising a, needle, a

horizontal ringaround the same provided with three lowerequidistant heels for hear in}: on a, plane, the said ring being concenon the longitudinal vertical plane of the planimeter and terminated in a collar which fits on the stem of the needle.

2. A planinieter comprising a bar, a stand of spatula shape at one end thereof, a needle the opposite end, a supporting base' around the needle consisting of a horizontal in the end opposite that provided with the spatula shaped stand and the stem of the needle having a reduced upper end fitted in said opening, said needle having a flange which bears on said bearing and also having a point at its lower end.

In Witness whereof I atiix my signature.

LUiS LARRAZABAL y FERNANDEZ. 

